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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org
Cc: linux-kernel@vger.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: [PATCH 1/2] Revert "x86/mm: Mark __pgtable_l5_enabled __initdata"
Date: Sat, 23 Jun 2018 01:08:40 +0300
Message-ID: <20180622220841.54135-2-kirill.shutemov@linux.intel.com> (raw)
In-Reply-To: <20180622220841.54135-1-kirill.shutemov@linux.intel.com>

This reverts commit e4e961e36f063484c48bed919013c106d178995d.

We need to use early version of pgtable_l5_enabled() in
early_identify_cpu() as this code runs before cpu_feature_enabled() is
usable.

But it leads to section mismatch:

cpu_init()
  load_mm_ldt()
    ldt_slot_va()
      LDT_BASE_ADDR
        LDT_PGD_ENTRY
	  pgtable_l5_enabled()
	    __pgtable_l5_enabled

__pgtable_l5_enabled marked as __initdata, but cpu_init() is not __init.

It's fixable: early code can be isolated into a separate translation
unit, but such change collides with other work in the area.
That's too much hassle to save 4 bytes of memory.

Return __pgtable_l5_enabled back to be __ro_after_init.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/kernel/head64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index a21d6ace648e..8047379e575a 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -44,7 +44,7 @@ static unsigned int __initdata next_early_pgt;
 pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
 
 #ifdef CONFIG_X86_5LEVEL
-unsigned int __pgtable_l5_enabled __initdata;
+unsigned int __pgtable_l5_enabled __ro_after_init;
 unsigned int pgdir_shift __ro_after_init = 39;
 EXPORT_SYMBOL(pgdir_shift);
 unsigned int ptrs_per_p4d __ro_after_init = 1;
-- 
2.17.1


  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-22 22:08 [PATCH 0/2] x86/mm: Fix 'no5lvl' handling in v4.18-rc1 Kirill A. Shutemov
2018-06-22 22:08 ` Kirill A. Shutemov [this message]
2018-06-23 12:30   ` [tip:x86/urgent] Revert "x86/mm: Mark __pgtable_l5_enabled __initdata" tip-bot for Kirill A. Shutemov
2018-06-22 22:08 ` [PATCH 2/2] x86/mm: Fix 'no5lvl' handling Kirill A. Shutemov
2018-06-23 12:31   ` [tip:x86/urgent] " tip-bot for Kirill A. Shutemov

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